Study of V2CTx-MXene Based Immunosensor for Sensitive Label-Free Impedimetric Detection of SARS-CoV-2 Spike Protein.

Rapid and reliable immunosensing is undoubtedly one of the priorities in the efficient management and combat against a pandemic, as society has experienced with the SARS-CoV-2 outbreak; simple and cost-effective sensing strategies are at the forefront of these efforts. In this regard, 2D-layered MXenes hold great potential for electrochemical biosensing due to their attractive physicochemical properties. Herein, we present a V2CTx MXene-based sensing layer as an integral part of a label-free immunosensor for sensitive and selective detection of the SARS-CoV-2 spike protein. The sensor was fabricated on a supporting screen-printed carbon electrode using Nafion as an immobilizing agent for MXene and glutaraldehyde, the latter enabling effective binding of protein A for further site-oriented immobilization of anti-SARS-CoV-2 antibodies. A thorough structural analysis of the sensor architecture was carried out, and several key parameters affecting the fabrication and analytical performance of the immunosensor were investigated and optimized. The immunosensor showed excellent electroanalytical performance in combination with an impedimetric approach and exhibited a low detection limit of only 45 fM SARS-CoV-2 spike protein. Its practical applicability was successfully demonstrated by measuring the spike protein in a spiked artificial nasopharyngeal fluid sample.

Study of Chitosan-Stabilized Ti3C2Tx MXene for Ultrasensitive and Interference-Free Detection of Gaseous H2O2.

The development of sensitive, selective, and reliable gaseous hydrogen peroxide (H2O2) sensors operating at room temperature still represents a remaining challenge. In this work, we have investigated and combined the advantageous properties of a two-dimensional Ti3C2Tx MXene material that exhibits a large specific surface area and high surface activity, with favorable conducting and stabilizing properties of chitosan. The MXene-chitosan membrane was deposited on the ferrocyanide-modified screen-printed working carbon electrode, followed by applying poly(acrylic acid) as an electrolyte and accumulation medium for gaseous H2O2. The sensor showed highly sensitive and selective electroanalytical performance for detecting trace concentrations of gaseous H2O2 with a very low detection limit of 4 µg m-3 (4 ppbv), linear response in the studied concentration range of 0.5-30.0 mg m-3, and good reproducibility with an RSD of 1.3%. The applicability of the sensor was demonstrated by point-of-interest detection of gaseous H2O2 during the real hair bleaching process with a 9 and 12% H2O2 solution.

Determination of 5-hydroxymethylfurfural using an electropolymerized molecularly imprinted polymer in combination with Salle.

Coffee, a beverage with a complex chemical composition, is appreciated for the sensory experience of its taste and aroma. The compound 5-(hydroxymethyl)-2-furfural (HMF) is essential for sensory characterization of the beverage, and is also used in the traceability of its production. In this work, a procedure combining salting-out assisted liquid-liquid extraction (SALLE) and an electropolymerized molecularly imprinted polymer (e-MIP) was developed for the detection and quantification of HMF in coffee samples. The sample preparation step using SALLE employed a combination of acetonitrile and phosphate-buffered saline, in a proportion of 70:30 (ACN:PBS), with addition of 0.02 g of NaCl. The new sensor (e-MIP) was prepared by electropolymerization of p-aminobenzoic acid onto a glassy carbon electrode (GCE) using cyclic voltammetry (CV). Analytical determinations were performed by differential pulse voltammetry (DPV). The linear regression correlation coefficient (r2) for the response was 0.9986. The limits of detection and quantification were 0.372 mg L-1 and 1.240 mg L-1, respectively. The repeatability and reproducibility values obtained were 6 and 10%, respectively. The recoveries for three concentration levels were between 97 and 101%. Analyses of different coffee samples showed that the HMF concentrations varied from 261.0 ± 41.0 to 770.2 ± 55.9 mg kg-1 in powdered coffee samples, and from 1510 ± 50 to 4445 ± 278 mg kg-1 in instant coffee samples. The advantages of this procedure, compared to other methods described in the literature, are its simplicity, easy operation, good selectivity and sensitivity, low cost, and minimal use of organic solvents.

Electroanalytical profiling of cocaine samples by means of an electropolymerized molecularly imprinted polymer using benzocaine as the template molecule.

The analysis of 'cutting' or additive agents in cocaine, like benzocaine (BZC), allows police analysts to identify each component of the sample, thus obtaining information like the drugs' provenience. This kind of drug profiling is of great value in tackling drug trafficking. Electropolymerized molecularly imprinted polymers (e-MIPs) on portable screen-printed carbon electrodes (SPCEs) were developed in this study for BZC determination. The MIPs' electropolymerization was performed on a carbon surface using the anaesthetic BZC as the template molecule and 3-amino-4-hydroxybenzoic acid (3,4-AHBA) as the functional monomer. The build-up of this biomimetic sensor was carefully characterized by cyclic voltammetry (CV) and optimized. Cyclic voltammetric investigation demonstrated that BZC oxidation had a complex and pH-dependent mechanism, but at pH 7.4 a single, well-defined oxidation feature was observed. The BZC-MIP interactions were studied by computer-aided theoretical modeling by means of density functional theory (DFT) calculations. The electroanalytical methodology was effectively applied to artificial urine samples; BZC molecular recognition was achieved with a low limit of detection (LOD) of 2.9 nmol L-1 employing square-wave voltammetry (SWV). The e-MIPs were then used to 'fingerprint' genuine cocaine samples, assisted by principal component analysis (PCA), at the central forensic laboratory of the Brazilian Federal Police (BFP) with a portable potentiostat. This electroanalysis provided proof-of-concept that the drugs could be voltammetrically 'fingerprinted' using e-MIPs supported by chemometric analysis.

Biosensing of D-dimer, making the transition from the central hospital laboratory to bedside determination.

Since the disclosure of the fibrinogen degradation mechanism, around half a century ago, a significant number of papers have been published related to the clinical relevance of D-dimer, a molecule immune to additional enzymatic decomposition by plasmin. Due to the obliquity of regulating blood coagulation in pathological events, the number of diseases and conditions associated with abnormal levels of D-dimer includes deep vein thrombosis, pulmonary embolism, sepsis, myocardial infarction, disseminated intravascular coagulation, among many others. D-dimer not only is an important player in medical diagnosis but also its role as a prognosis biomarker is being revealed. However, the number of analytical alternative methods has not accompanied this trend, even though novel simple point-of-care devices would certainly boost the relevance of D-dimer in emergency medicine. Some reasons for that could be related to the fact that D-dimer is a challenging analyte present in complex samples like blood. In this manuscript, subsequent to a fibrinogen degradation process introduction, it is provided a historical overview of the early D-dimer assays, followed by an extended focus on innovative solutions, with a spotlight on the electrochemical bioanalytical devices. The discussion is accompanied with a critical analysis and concluding thoughts concerning future perspectives.

Cell Metabolism Control Through O-GlcNAcylation of STAT5: A Full or Empty Fuel Tank Makes a Big Difference for Cancer Cell Growth and Survival.

O-GlcNAcylation is a post-translational modification that influences tyrosine phosphorylation in healthy and malignant cells. O-GlcNAc is a product of the hexosamine biosynthetic pathway, a side pathway of glucose metabolism. It is essential for cell survival and proper gene regulation, mirroring the metabolic status of a cell. STAT3 and STAT5 proteins are essential transcription factors that can act in a mutational context-dependent manner as oncogenes or tumor suppressors. They regulate gene expression for vital processes such as cell differentiation, survival, or growth, and are also critically involved in metabolic control. The role of STAT3/5 proteins in metabolic processes is partly independent of their transcriptional regulatory role, but is still poorly understood. Interestingly, STAT3 and STAT5 are modified by O-GlcNAc in response to the metabolic status of the cell. Here, we discuss and summarize evidence of O-GlcNAcylation-regulating STAT function, focusing in particular on hyperactive STAT5A transplant studies in the hematopoietic system. We emphasize that a single O-GlcNAc modification is essential to promote development of neoplastic cell growth through enhancing STAT5A tyrosine phosphorylation. Inhibition of O-GlcNAcylation of STAT5A on threonine 92 lowers tyrosine phosphorylation of oncogenic STAT5A and ablates malignant transformation. We conclude on strategies for new therapeutic options to block O-GlcNAcylation in combination with tyrosine kinase inhibitors to target neoplastic cancer cell growth and survival.

Bacterial cellulose-lignin composite hydrogel as a promising agent in chronic wound healing.

Lignins and lignin-derived compounds are known to have antibacterial properties. The wound healing agents in the form of dressings produce faster skin repair and decrease pain in patients. In order to create an efficient antimicrobial agent in the form of dressing in the treatment of chronic wounds, a composite hydrogel of bacterial cellulose (BC) and dehydrogenative polymer of coniferyl alcohol (DHP), BC-DHP, was designed. Novel composite showed inhibitory or bactericidal effects against selected pathogenic bacteria, including clinically isolated ones. The highest release rate of DHP was in the first hour, while after 24 h there was still slow release of small amounts of DHP from BC-DHP during 72 h monitoring. High-performance liquid chromatography coupled with mass-spectrometry showed that BC-DHP releases DHP oligomers, which are proposed to be antimicrobially active DHP fractions. Scanning electron microscopy and atomic force microscopy micrographs proved a dose-dependent interaction of DHP with BC, which resulted in a decrease of the pore number and size in the cellulose membrane. The Fourier-transform infrared absorption spectra of the BC-DHP showed that DHP was partly bound to the BC matrix. The swelling and crystallinity degree were dose-dependent. All obtained results confirmed BC-DHP composite as a promising hydrogel for wounds healing.